This invention relates to measuring corrosion rates and it relates more particularly to instruments and electro-chemical techniques used in the study of corrosion processes, and most particularly to the measurement of the total corrosion rate of a metal subjected to a galvanic current.
Galvanic coupling of metals is unavoidable and must be taken into account in monitoring the corrosion of metals in a great variety of equipment and industrial plants. It had been assumed in the past that the determination of galvanic currents had to be done on two separate isolated electrodes via an ammeter, preferably a zero resistance ammeter. With this method, however, one only measures the acceleration of corrosion due to the galvanic influence but not the actual corrosion rate of the metal in question, since the latter per definition occurs without current in any external circuit. This is a distinct drawback, since galvanic action may, and in many cases does, cause a shift of the corrosion potential of the metal in the anodic (positive) direction. This, in turn, can cause a breakdown of an inhibitor (desorption) causing the metal to corrode much more heavily, an effect which would not necessarily be detected with the zero resistance ammeter.
It is an object of this invention to provide a method for determining the total corrosion rate of a metal subjected to a galvanic current.
It is a further object of this invention to provide a test electrode for use in measuring such total corrosion rate.
It is still an additional object of this invention to provide a probe including such a test electrode for use in measuring such total corrosion rate.
Other objects of the invention will become apparent from the following description.